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<th nowrap width="1%" height="32">P0039</th>
<th nowrap width="98%">AVSImagePlayer</th>
<th nowrap width="1%">26th January 1999</th>
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<p><b>Author:</b> Fernand Alcatrao
<b>Version:</b> 1.0
<b>Path:</b> iac_proj/ximg_ply/</p>
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<h1>AVSImagePlayer</h1>
<h3>Synopsis</h3>
<p>
Animates a number of AVS x format image files stored in memory or on
disk.
</p>
<p>
<hr>
<pre>
module AVSImagePlayer < src_file="ximg_ply.cxx",
build_dir="iac_proj/ximg_ply",
out_src_file="gen.cxx",
out_hdr_file="gen.hxx",
cxx_name="xImgPlay",
cxx_members="private:
friend void AVSImagePlayer_LoopFuncTmp(char *arg);
void LoopFunc(void);
int ReadImages(void);
int ReadImage(int image_no, int data_array_index,
char *module_name); ",
cxx_hdr_files="fld/Xfld.h"> {
ImagePlayerParams+read+write+req &ImagePlayerParams<NEportLevels={2,0}>;
int trigger_run<NEportLevels={2,0}>;
int trigger_stop<NEportLevels={2,0}>;
int+read+req data_array_size = 1;
Data_Array+write+nonotify+nosave Data_Array[data_array_size] {
veclen = 4;
id = 669;
values+byte;
null_value+byte;
min+byte;
max+byte;
min_vec+byte;
max_vec+byte;
};
int node_data_index => switch((ImagePlayerParams.access_mode + 1),
0,ImagePlayerParams.count);
Mesh_Unif+Node_Data+write+nonotify out<NEportLevels={0,2}> {
ndim = 2;
nspace = 2;
points => { {0,0}, {(dims[0] - 1),(dims[1] - 1)} };
nnode_data = 1;
&node_data => Data_Array[node_data_index];
};
GDM.DataObject DataObject {
in => out;
Obj<NEportLevels={0,3}>;
};
cxxmethod+req image_player_run( trigger_run+read+notify+req );
cxxmethod+req image_player_stop( trigger_stop+read+notify+req );
};
</pre>
<hr>
</p>
<h3>Description</h3>
<p>
AVSImagePlayer is a low level module that is able to read in image files
in the AVS x format and then animate them from either memory or by
loading each image as it is required. The image filenames are specified
by using a C-style format-string and a number of parameters. The module
is also able to control the rate at which the images are animated,
whether the animation runs forward or backwards and whether the
animation cycles continously. The images are output as both a uniform
mesh with colours represented by node data, and a renderable DataObject
that is generated from the uniform mesh.
</p>
<h3>Inputs</h3>
<p>
<i><b>trigger_run</b></i>
</p>
<p>
When updated this parameters triggers the start of the animation. The
animation then runs until the trigger_stop parameter is updated, or
until all images have been displayed if the animation is not cycling.
When updated the parameter triggers the loading of image files into
memory, should this be necessary.
</p>
<p>
<i><b>trigger_stop</b></i>
</p>
<p>
When updated this parameter halts the animation. The animation stops at
the current frame. This parameter does not reset the animation to either
the first or last frames.
</p>
<p>
<i><b>&ImagePlayerParams</b></i>
</p>
<p>
Reference to the parameter block, which contains real instances of the
parameters for the AVSImagePlayer function.
</p>
<p>
<i><b>ImagePlayerParams.file_format</b></i>
</p>
<p>
Filename formatting string that specifies the filenames of the image
files that are to be loaded. The parameter is of type string. This
parameter uses a C-style formatting expression to generate indexed
filenames.
</p>
<p>
Therefore setting <TT>file_format</TT> to <TT>"Imag%d.x"</TT> will
generate filenames of the form <TT>"Image0.x"</TT> with no leading
characters; whilst setting the parameter to <TT>"Image%04d.x"</TT> will
generate filenames which are padded with zeros to be 8 characters long
(i.e. <TT>"Imag0001.x"</TT>). More information can be found in any C
reference book.
</p>
<p>
<i><b>ImagePlayerParams.nb_images</b></i>
</p>
<p>
Total number of images that are to be animated. This parameter is of
type int. The animation will stop or repeat as appropriate when this
many frames have been displayed.
</p>
<p>
<i><b>ImagePlayerParams.first_image</b></i>
</p>
<p>
Index number of first image to be animated. This parameter is of type int.
</p>
<p>
<i><b>ImagePlayerParams.step</b></i>
</p>
<p>
Value that the index number should be incremented by during each
iteration of the animation loop. This parameter is of type int.
</p>
<p>
<i><b>ImagePlayerParams.access_mode</b></i>
</p>
<p>
Specifies whether images should be animated from memory or from disk.
This parameter is of type int. Setting the parameter to 0 specifies that
each image should be read from disk immediately before it is displayed.
Setting the parameter to 1 specifies that all the images should be
loaded into memory before the animation begins and displayed directly
from memory.
</p>
<p>
<i><b>ImagePlayerParams.run_mode</b></i>
</p>
<p>
Specifies how the animation should be performed. This parameter is of
type int. There are four possible values for this parameter:-
</p>
<dl compact>
<dt>0 <dd>Play forwards until last frame is reached
<dt>1 <dd>Play forwards continously, cycling to start when last frame is reached
<dt>2 <dd>Play backwards until first frame is reached
<dt>3 <dd>Play backwards continously, cycling to end when first frame is reached
</dl>
<p>
<i><b>ImagePlayerParams.fps</b></i>
</p>
<p>
Number of frames per second that the images should be animated at. This
parameter is of type float. This is the ideal number of frames per
second, if the system is unable to achieve this value then the animation
will run at a lower rate.
</p>
<p>
<i><b>ImagePlayerParams.nsec_before</b></i>
</p>
<p>
Specifies the number of seconds that the animation should wait at the
starting frame before the animation is restarted. This parameter only
applies when the animation is cycling. The parameter is of type int.
</p>
<p>
<i><b>ImagePlayerParams.nsec_after</b></i>
</p>
<p>
Specifies the number of seconds that the animation should wait at the
ending frame before the animation returns to the starting frame. This
parameter only applies when the animation is cycling. The parameter is
of type int.
</p>
<p>
<i><b>ImagePlayerParams.count</b></i>
</p>
<p>
The index number of the currently displayed image. This parameter is of
type int. Setting this parameter will cause the currently displayed
image to change immediately.
</p>
<p>
<i><b>ImagePlayerParams.real_fps</b></i>
</p>
<p>
Number of frames per second that the animation is actually running at. This
parameter is of type string. The parameter is intended for display only
and to ease display the number of frames per second is included along with an
appropriate message by the module.
</p>
<h3>Outputs</h3>
<p>
<i><b>out</b></i>
</p>
<p>
Field data containing the currently displayed image. The image is
represented by a uniform mesh. The colour of each pixel is represented
by a vector of length 4 (i.e. alpha, red, green, blue) at each node data
point.
</p>
<p>
<i><b>obj</b></i>
</p>
<p>
The directly renderable output field of the AVSImagePlayer module. This
contains a DataObject object that can be rendered by the standard data
viewers. The DataObject is generated directly from the field data
created from the currently displayed image.
</p>
<h3>Utility Macros</h3>
<p>
The low-level AVSImagePlayer module is used in the User Macro
imagePlayer. Additionally, this macro also uses the ImagePlayerParams
parameter block group object, as does the ImagePlayerUI UI Macro.
</p>
<h3>Example</h3>
<p>
An example application AVSImagePlayerEg is provided, which uses the
animation module to display a sequence of images generated for a
Meteorological Office presentation on global warming.
</p>
<h3>Files</h3>
<p>
<I>iac_proj/ximg_ply/iplymods.v</I> contains the ImagePlayerParams group
and the AVSImagePlayer module V definitions.
</p>
<h3>Other Notes</h3>
<p>
The low-level AVSImagePlayerMods library containing the module AVSImagePlayer does not
specify a process. By default the <tt>express</tt> process will be used.
</p>
<h3>Authors</h3>
<p>
<pre>
Fernand Alcatrao
</pre>
</p>
<h3>Modifications</h3>
<p>
<pre>
Andrew Dodd
</pre>
</p>
<h3>Contact</h3>
<p>
<pre>
International AVS Centre
Manchester Visualization Centre
Manchester Computing
University of Manchester
Oxford Road
Manchester
United Kingdom
M13 9PL
</pre>
</p>
<h3>See Also</h3>
<p>
ImagePlayerParams, ImagePlayerUI, imagePlayer
</p>
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<td width="100%"> Last Updated:
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26th November 2002
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